Archery bow with draw force multiplying attachments



H. w. ALLEN Dec. 30, 1969 ARCHERY BOW WITH DRAW FORCE MULTIPLYINGATTACHMENTS 2 Sheets-Sheet 1 Filed June 23, 1966 MA W s S M m Dec. 30,1969 "H. w. ALLEN I 3,486,495

ARCHERY BOW WITH ITRAW FORCE MULTIPLYING ATTACHMENTS Filed June 23, 19662 Sheets-Sheet 2 INVENTOR Hal/ess W. Allen United States Patent3,486,495 ARCHERY BOW WITH DRAW FORCE MULTIPLYING ATTACHMENTS Holless W.Allen, Kansas City, Mo. (Billings, Mo. 65610) Filed June 23, 1966, Ser.No. 559,761

Int. Cl. F41b /00 US. Cl. 124-24 14 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to improvements in shooting bows and, morespecifically, to a bow having variable purchase devices mounted on thelimb tips thereof and operable by the bowstring to increase the energyof the bow when drawn without increasing the length of the draw or theholding force required in the drawn positon.

Shooting bows in widespread use at the present time are available in anumber of different types and configurations; however, the archers howhas not changed in basic design since the development of the long bowmany ceturies ago. Although a number of refinements have improved theefliciency of the modern bow as compared with its historicalpredecessor, the essential shotting characteristics remain the same inthat the force required to draw the bowstring increases as the limbs areflexed to a maximum level at full draw. Thus, the maximum pull isrequired when the archer sets for the shot, thereby limting the strengthof the bow which may be handled by a particular individual since anarcher must be capable of holding the bow on target while simultaneouslyexerting maximum pull on the bowstring.

Another important limitation in present bow design is the maximum energywhich may be stored in the limbs. The bow must be shot after the nockingpoint is moved a fixed distance, referred to as the standard draw,regardless of the strength of the bow. Therefore, in order to increasethe energy of the bow, the limbs are stiffened to require a greater pullat the standard draw. Manifestly, here again, the physical capabilitesof the archer are controlling.

It is, therefore, the primary object of this invention to increase arrowspeed and imapct by providing a bow which, for a given strength, iscapable of storing greater energy when drawn without requiring that themaximum pull weight of the bow be increased.

It is also an important object to provide a bow having a lesser pullweight at full draw than at an intermediate drawn position, so that themaximum force applied by the archer to the bowstring will not berequired to hold the string in the fully drawn position.

Another important object is to provide a bow having variable purchasedevices on the limbs thereof which transmit the force applied to thebowstring to the limb tips as the bowstring is drawn, such devicesserving to require the archer to apply added force at the commencementof the draw to effect an increased energy buildup in the limbs so that,at full draw, greater energy will be imparted to the limbs although alesser force is required to hold the string.

3,486,495 Patented Dec. 30, 1969 Still another important object is toprovide a bow which, by virtue of the force and energy characteristicsreferred to above, will shoot an arrow by the application of forcethereto which does not reach a maximum until after the releasedbowstring has traveled a distance toward 1ts rest position so thatimproved flight characteristics will be imparted to the arrow.

Furthermore, it is a specific object to provide a bow having an energygraph characteristic which is generally ellipsoidal in configuration,rather than triangular as in conventional bows so that, for limbs of agiven stiffness, greater limb tip travel, and hence increased energy,will be obtained for a standard draw.

Additionally, it is an aim of this invention to provide limbs which areadjustable with respect to the handle section of the bow in order topermit relaxing of the limbs during nonuse and adjustment of the pullweight of the bow.

In the drawings:

FIGURE 1 is a side elevational view of the bow;

FIG. 2 is a front view of the bow;

FIG. 3 is a detaile of the eccentric member on the upper limb of the bowas seen in FIG. 1;

FIG. 4 is a front view of the structure shown in FIG. 3;

FIG. 5 is a detail, plan view of the member shown in FIG. 3;

FIG. 6 is a side elevational view of the bow taken from the oppositeside as compared with FIG. 1, and showing the intermediate and drawnpositions of the bowstring;

FIG. 7 is a side elevational, detail view of a modified form of theeccentric member;

FIG. 8 is a bottom View of the structure shown in FIG.

FIG. 9 is a graph illustrating the characteristics of the bow utilizingthe eccentric members illustrated in FIGS. l-6; and

FIG. 10 is a graph illustrating the operation of the bow utilizing themodified eccentric members illustrated in FIGS. 7 and 8.

A how 20 is provided with a riser or handle section 22 having an arrowshelf 23 and a pair of upper and lower limbs 24 and 26 respectively,extending outwardly thereform. Upper li-mb 24 has a tip 28 which isbifurcated as illustrated in FIG. 2 and mounts a cross pin 30 upon whichan eccentric pulley member 32 is rotatably mounted. Similarly, lowerlimb 26 has a bifurcated tip 24 which carries a cross pin 36 upon whicha pulley member 38 is eccentrically mounted.

A bowstring 40 is trained around members 32 and 38 .to present a centralstretch 42 and a pair of end stretches 44 and 46. An adjustable coupling48 connects the end 50 of stretch 44 to tip 28 at cross pin 30, anadjustable coupling 52 connecting end 54 of stretch 46 to tip 34 atcross pin 36. The central, outer stretch 42 is provided with a serving56 which presents the nocking point 58 of the bowstring.

The upper portion of handle section 22 is configured to present a pairof parallel side members 60 which define a channel therebetweenreceiving the lower end portion of limb 24. A pivot pin 62 extendsthrough members 60 and limb 24 and mounts the latter for swingingmovement about the axis of the pin. A threaded shank 64 (FIG. 6) extendsthrough an opening 66 in the lower end of limb 24 and is held by a nut68 recessed into handle section 22 as illustrated. An adjustment knob 70is rigid with the outer end of shank 64, the base of the channel formedby side members 60 being arcuate in configuration as indicated at 72 inFIG. 6. In like fashion, the upper end of lower limb 26 is receivedbetween the lower side members 74 for swinging movement about a pivotpin 76 upon rotation of knob 78.

Member 32 is of generally oval-shaped configuration and is grooved (seeFIG. to present a pair of parallel bowstring tracks 80 and 82 whichtraverse a generally oval-shaped course. Track 82 at the right-band edgeof member 32 (as viewed in FIGS. 1, 3 and 5) is more deeply recessedinto the periphery of the member than track 80, and thus is shorter inlength. Stretch 46, when the bow is at rest as shown in FIGS. l4,contacts track 80 at the left end of member 32 (as viewed in FIGS. 3 and5), and then the bowstring makes approximately a two-thirds wrap beforecrossing over to track 82. Then, the bowstring follows track 82 forapproximately a three-quarter wrap and emanates from device 32 topresent central stretch 42. Crossover of the bowstring from track 82 totrack 80 is permitted by a notch 84 in the periphery of member 32 whichintercommunicates the two tracks.

Member 38 is identical in construction to member 32 except that thetracks therein are reversed with respect to the showing of FIG. 5 todispose the shorter track of member 38 in the same plane as track 82 ofmember 32, and the longer track thereof in the same plane as track 80.This is necessary to properly align the tracks since the lower member 38is inverted with respect to upper member 32. Except for the direction ofwrap, the bowstring is received by member 38 in the same manner asmember 32 with central stretch 42 emanating from the shorter track.

FIGS. 7 and 8 illustrate a modified pulley member 86 of circularconfiguration rotatable on the pin 30 carried by tip 28. Thecircumferential periphery of member 86 is grooved to provide twocircular, parallel bowstring tracks 88 and 90 of equal length. Thebowstring is wrapped around member 86 one and one-half times with acrossover at notch 92. Member 86 is used in conjunction with a lowereccentric pulley member (not shown) of identical configuration, suchpulley members being substituted for members 32 and 38 in the modifiedform of the invention. When the bow is at rest, notch 92 is disposed asshown at the lowermost point of member 86; conversely, however, thecrossover point for the lower member would be at the uppermost point onits circumferential periphery when the bow as at rest. In all respects,therefore, except for the track configuration, the circular pulleymembers are employed in the same manner as members 32 and 38.

FIGURE 9 illustrates the operation of the bow using the eccentricmembers illustrated in FIGS. 1-6. The x axis of the graph is labeled Dand plots the distance that nocking point 58 is drawn. The force appliedto nocking point 58 by the archer is divided into two components F and Fwhich are identical in magnitude at any distance D. F represents theforce required to flex limb 24, while force F represents the forcerequired to flex limb 26.

Curves 94 and 96 begin at the origin and terminate at a draw distancedesignated 98. This distance 98 represents a standard draw illustratedin FIG. 6 by the broken line representation of central stretch 42. Thetwo curves 94 and 96 reach coordinates representing maximum force atpoints 100 and 102, respectively. It will be appreciated, therefore,that the area enclosed by curves 94 and 96 is ellipsoidal inconfiguration and represents the total energy stored in limbs 24 and 26at a standard draw.

Lines 104- and 106 emanating from the origin represent the energydiagram produced by a conventional bow utilizing a bowstring directlyjoined at its ends to the limb tips. It will be appreciated that, at astandard draw, the triangle defined by lines 104 and 106 and theinterconnecting line through point 98, is of less area than theaforementioned area between curves 94 and 96. In order to reach anequivalent energy level, the draw would have to be increased to adistance 108 as illustrated by the broken line projection of lines 104and 106.

At this juncture, it is instructive to note that the energy stored inthe bow at a standard draw is reater than in a conventional bow and,furthermore, that the force required to hold the bowstring at full drawis both less than the maximum pull 100, 102 and appreciably less thanthe pull weight of a conventional bow, which would also be equal to 100,102. This holding force at full draw is represented by the ordinatesterminating at 110 and 112; thus, FIG. 9 vividly illustrates that, for asubstantially decreased pull weight at full draw, the bow of the instantinvention yields greater power through increased energy storage in limbs24 and 26, such energy being imparted by the archer during movement ofnocking point 58 from the rest position (shown in FIG. 1) to the drawnposition illustrated in FIG. 6.

The full lines in FIG. 6 show nocking point 58 in its intermediateposition where the drawing force or pull is represented in FIG. 9 by thepoints 100, 102. During the draw from the rest position to suchintermediate position, members 32 and 38 rotate about pins 30 and 36 asillustrated with member 32 rotating in a counterclockwise direction andmember 38 rotating in a clockwise direction, as viewed in FIG. 6. Ineffect, therefore, the portions of the eccentric members of longerradius swing outwardly and rearwardly toward the archer during thisfirst portion of the draw from the rest to the intermediate position.

The tension of bowstring 40 in cooperation with the crossover notches inmembers 32 and 38 prevents slippage of the bowstring in the tracksformed in members 30 and 32. Thus, the members are forced to traversethe paths illustrated and are effective to increase the force requiredto draw the bow during this initial displacement of nocking point 58.This additional force is converted into increased displacement of limbtips 28 and 34.

As the archer continues to draw the bow and shifts nocking point 58 tothe drawn position illustrated in broken lines, member 32 and 38 effecta gain in mechanical advantage and permit easier drawing of the bow.This is illustrated by a comparison of the full and broken linepositions of the members in FIG. 6 where it may be seen that bothmembers continue rotation until their longest radii point in the generaldirection of the archer. The leverage obtained is by virtue of thelength of each member from its axis of rotation to the end thereofremote from the axis to which central stretch 42 is effectivelyconnected after the nocking point is drawn to the intermediate position.It will be noted that initially when the bow is at rest, end stretches44 and 46 of the bowstring emanate from the remote end portions ofmembers 32 and 38, while after the intermediate position is reached,central stretch 42 emanates from such remote ends.

The effect produced as the archer draws the bow is perhaps bestvisualized with reference to curves 94 and 96 of FIG. 9. At the outsetof the draw the ordinate values of the curves increase quite rapidly andthus exhibit that the reqired drawing force must be progressivelyincreased to shift the nocking point 58 from the rest position to theintermediate position represented by points and 102. As the intermediateposition is approached, the required force increases leess rapidly untilthe maximum is reached at points 100 and 102. After the intermediateposition, as the nocking point is shifted to the drawn position, therequired applied force progressively decreases to a value represented byordinates and 112, the holding force at standard draw.

FIGURE 10 illustrates the operation of the bow utilizing the eccentricmembers shown in FIGS. 7 and 8. The operation is essentially the same asdescribed above, but the energy diagram produced differs in that a morelinear force increase is produced between the rest and the intermediateor maximum force position of nocking point 58 illustrated at points 114and 116 on the graph. Here again, however, the holding force at fulldraw illustrated at 118 and 120 is substantially less than for aconventional bow, and the energy imparted to the limbs is greater at thestandard draw distance 122. Lines 124 and 126 represent the draw of aconventional bow, which would have to be extended to a distancerepresented by point 128 in order to impart the same energy to the limbsas produced by the instant invention at the standard draw.

Although the addition of the eccentric pulley members to the limb tipsnecessarily incerases the mass and therefore the inertia of the limbs,this is more than offset by the use of shorter limbs of increasedstrength or stilfness. Limbs of approximately three times the strengthof conventional bow limbs are preferred. This results in a correspondingreduction of limb tip travel required for a given amount of bow energy.The three line lacing of the bowstring provides a 3:1 mechanicaladvantage (ideally) and, in cooperation with the eccentric pulleys,enables the archer to flex the limbs and draw the bowstring to thestandard draw.

Relaxing of the limbs during nonuse is facilitated by adjustment knobs70 and 78 which may be rotated to release the limbs for swingingmovement about pivot pins 62 and 76. Additionally, knobs 70 and 78provide a means of adjusting the pull weight of the bow to suit theindividual archer. In FIG. 6 it may be seen that limb 24 is illustratedin a position requiring maximum pull since the lower end thereof isflush with base surface 72. To reduce the pull weight, shank 64 isrotated in a direction to permit counterclockwise displacement of limb24 about pin 62 (as viewed in FIG. 6) to allow the lower end of the limbto move away from surface 72 to a desired degree.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In a shooting how:

a handle section provided with a pair of outwardly extending resilientlimbs presenting a pair of spaced limb tips;

a bowstring having a nocking point; and

structure coupling said bowstring with said tips for movement of saidpoint from a rest position to a drawn, limb-flexing position uponapplication of drawing force thereto,

said structure having means for establishing an intermediate position ofsaid point between said rest and drawn positions where the applied forcerequired to hold the point in said intermediate position is greater thanthe force required to hold the point in the drawn position, whereby toincrease the rate of buildup of energy in the bow between the restposition of the point and the intermediate draw position while alsodecreasing the holding force at full draw to a value less than the forceat intermediate draw.

2. The invention of claim 1,

said means varying the ratio of applied force to the correspondingdisplacement of the point as the latter is shifted from the restposition to the drawn position.

3. The invention of claim 1,

said means permitting movement of said point to the drawn position bythe application of forces of continuously decreasing magnitude after thepoint reaches said intermediate position and until it reaches the drawnposition.

4. The invention of claim 1,

said means, during initial movement of said point away from the restposition, efiecting flexure of said limbs in response to applied forcesof relatively rapidly increasing magnitude, and subsequently permittingmovement of said point from the intermediate position to the drawnposition by the application of forces of continuously decreasingmagnitude.

5. The invention of claim 4,

said means, during movement of said point from the rest position to theintermediate position, etfecting flexure of said limbs in response toapplied forces of continuously less rapidly increasing magnitude as thepoint approaches the intermediate position.

6. The invention of claim 1,

said means including a pair of variable purchase devices operable.associated with respective limbs,

said bowstring being connected to said devices for operating the latterto flex the limbs as the point is shifted from the rest position to thedrawn position.

7. The invention of claim 1,

said means including a pair of variable leverage com ponents rotatablymounted on respective tips,

said bowstring being connected to said variable leverage components forshifting each of the latter through a first, tip travel increasingangular displacement during movement of said point from the restposition to said intermediate position, and through a second, mechanicaladvantage gaining angular displacement as the point is shifted from theintermediate position to the drawn position.

8. The invention of claim 7,

each of said variable leverage components comprising an eccentricmember,

the axes of rotation of the members being in parallelism and extendingtransversely of the direction of flexure of said limbs,

said bowstring having a pair of ends and being trained around saidmembers to present a central stretch and a pair of end stretchesextending between the limbs, whereby the bowstring is wrapped aroundeach member,

said coupling structure further including means fastening the ends ofthe bowstring to respective limbs,

said members being provided with means preventing slippage of thebowstring thereon,

said central stretch presenting said point.

9. The invention of claim 8,

each of said members having a bowstring engaging track of generallyoval-shaped configuration disposed in eccentric relationship to the axisof rotation thereof.

10. The invention of claim 8,

each of said members having a bowstring engaging track of circularconfiguration disposed in eccentric relationship to the axis of rotationthereof.

11. The invention of claim 1,

said handle section having a pair of pivots supporting respective limbsremote from said tips thereof for swinging movement of each limb along apath of travel extending rearwardly of the section; and

adjustable means interconnecting said limbs and said section forreleasably securing the same together with the limbs disposed inselected positions relative to said section, whereby to permit relaxingof the limb during nonuse and adjustment of the pull weight of the bow.

12. In a shooting how:

a handle section provided with a pair of outwardly extending, resilientlimbs presenting a pair of spaced limb tips;

a bowstring having a nocking point;

a guide for said bowstring on each of said tips respectively,

said bowstring having a central stretch spanning said guides andprovided with said point, and further having a pair of end stretches,

each of said end stretches extending across the limbs fron acorresponding guide to the opposite limb; an

means fastening said end stretches to the bow at their terminations.

13. The invention of claim 12,

each of said end stretches diverging from the limb proximal to thecorresponding guide as the opposite limb is approached.

7 8 14. The invention of claim 1, References Cited said means includinga pair of rotatable, variable UNITED STATES PATENTS leverage componentsoperably associated wlth respective limbs, 85,874 1/ 1869 Tilden 124-24said bowstring being connected to said components for 261,610 7/1882Howe shifting each of the latter through a first angular 0 2,307,0211/1943 Cordrey et a1 124 23 displacement increasing the travel of therespective 2,957,470 10/1960 Bama 124-44 tip during movement of saidpoint from the rest 3,207,146 9/1965 Grable 124*24 position to saidintermediate position, and through a second, mechanical advantagegaining angular dis- 1 RICHARD PINKHAM Pnmary Exammer 0 placement as thepomt is shifted from the mter- WILLIAM R. BROWNE,Ass1stant Examinermediate position to the drawn position.

Disclaimer 3,486,495.-H0lless W. Allen, Kansas City, Mo. ARCHERY BOWWITH DRAWV F ORCE MULTIPLYING ATTACHMENTS. Patent dated Dec. 30, 1969.Disclaimer filed June 18, 1974, by the assignee, Allen Archery, Inc.Hereby enters this disclaimer to claims 1, 2 and 11 of said patent.

[Oficz'al Gazette May 20, 1.975.]

